Microporous membrane hollow fibers (MMHF) have become standard in blood oxygenating devices used for short term cardiorespiratory support procedures. These devices used for short term cardiorespiratory support procedures. These devices have become popular mainly because of enhanced gas exchange due to the convective mixing induced by the blood flowing on the outside of thousands of tiny hollow fibers. This property allows for designing highly efficient gas exchange devices in relatively compact volumes. Yet MMHF suffer from plasma leakage when they are used for extended periods of time, and from gas embolization when the gas side pressure exceed the blood side pressure, exceed the blood side pressure. Thus the compactness and effectiveness of the MMHF, plus the ability of solid silicone membranes to withstanding plasma leakage and gas embolization are desirable properties in a membrane designed blood oxygenation. We have devised a technique that will allow for the fabrication of a solid silicone membrane configured in a uniform hollow three-dimensional array, such that gas can flow in the inside and blood on the outside of this hollow array. This design allows for uniform convective mixing, and unlimited flexibility in design parameters. In Phase II we proposed to further develop the fabrication technique and to evaluate the membrane design parameters for gas exchange and hemodynamic performance. PROPOSED COMMERCIAL APPLICATIONS: The proposed membrane will significantly enhance safety and performance of blood oxygenators used for cardiopulmonary bypass operations. There are over 300,000 disposable oxygenators used in the US every year.